In a process of fabricating an OLED display panel, in order to ensure the lifetime of an OLED device, an organic layer in the OLED device is typically insulated from vapor and oxygen in ambient air, and in the related art, an area to be sealed enclosed by an upper sealing glass substrate and a lower sealing glass substrate for packaging the OLED device is filled with a sealing glass frit (see FIG. 1), and then the sealing glass frit is heated by a moving laser beam and melted to make the OLED device airtight, where the sealing glass frit is typically a low-temperature sealing glass frit.
The thermal expansion coefficient of the sealing glass substrates of the OLED device is in the range between 30×10−7/° C. and 45×10−7/° C., and the sealing glass frit is a mixture of glass powder with a low melting point and a low thermal expansion coefficient and a filler. If the thermal expansion coefficient of the sealing glass frit is significantly different from the thermal expansion coefficient of the sealing glass substrates, then warping and breakage may occur when the sealing glass substrates are sealed by the sealing glass frit, or breakage may occur in the sealing glass substrates packaging the OLED device being illuminated by intensive light, thus resulting in a low yield of the packaged OLED device.
Generally there is a high positive thermal expansion coefficient of the glass powder, and in order to improve the yield of the packaged OLED device, typically a material with a negative thermal expansion coefficient is selected as the filler, e.g., eucryptite, cordierite or another negative thermal expansion material. However it may be difficult to control the thermal expansion coefficient of the sealing glass frit into which such a filler and the glass powder is mixed, and micro-breakage may tend to occur at the sites where the OLED device is packaged by the sealing glass frit including the filler, thus degrading the strength of the sealing material as a whole.
Consequently, it may be difficult to control the thermal expansion coefficient of the sealing glass frit in the related art because the filler is a negative thermal expansion material, which may degrade the yield of the packaged OLED device.